Digital Video - November 2007 - (Page 26) DV 101 A lighthouse scene shot first without (below), and then with (above), Tiffen’s circular polarizer (inset) for increased blue sky saturation. LENS FILTRATION OUR NEW EDUCATIONAL SERIES KICKS OFF WITH A PRIMER ON CORRECTION, CONTRAST AND EFFECTS FOR VIDEO CAMERAS. BY JAY HOLBEN T he farthest many videographers delve into lens filtration is a UV filter constantly affixed to their lens. Filters, for many, seem to be a terrifying undiscovered country. In this inaugural DV 101 column, I’ll try to demystify the art and science of lens filtration. Filters come primarily in two main shapes: circular and square (or rectangular). Circular filters are designed to screw directly onto the threaded rings on your lens, whereas square filters require a matte box to hold them in place. The benefit to certain square filters is that you can position them more precisely in front of the lens. This is beneficial for graduated filters that have transitions from a clear to an effect, or from one effect to another, so that you can precisely position the transition. Typical rectangular sizes are 4 in. x 4 in., 4 in. x 5.125 in. (called Panavision) and 6 in. x 6 in. To get the most versatility from your filters, it’s always best to have a matte box and a filter size that easily covers all of your lenses. Filters themselves are made of different types of materials. Most are glass, but some less expensive alternatives are made of dv november 2007 plastic or resin. If you’re going with a screw-on filter, you need to know the diameter of your lens to know which filter size to choose. Most lenses have this information printed right on them. The diameter symbol is an oval with a diagonal line through it—this is followed by a number, usually in millimeters. That’s your filter size. www.dv.com 26 http://www.dv.com
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